Answer:
The southwestern Pacific Plate has been subducting under the Indo-Australian Plate at the Tonga Trench since the middle of the Eocene era.
Explanation:
- The lithosphere-asthenosphere boundary (hereafter it is called as LAB), separating the lithosphere and the asthenosphere
, is an important mechanical interface of the Earth’s interior. The LAB has also been termed as Gutenberg (G) discontinuity that defines the top of the low velocity zone in the upper mantle.
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The southwestern Pacific Plate has been subducting under the Indo-Australian Plate at the Tonga Trench since the middle of the Eocene era. The present convergence rate between two plates are up to 200–250 mm/a and it is faster in the northern part than in the southern part. The Tonga area contains two-thirds of all deep earthquakes in the world, and comprises the zones of the deep slab subduction, the island arc magmatism and the back-arc basin spreading.
- Numerous seismologists reported that the cold subduction slab enters into the deep mantle, lowers mantle and induces the uplift of the 410 km discontinuity and the depression or stratification of the 660 km discontinuity. Seismic imaging studies proposed that the obvious low velocity zone above the subducted slabs is associated with the dehydration and de-carbonation of the slabs.
Learn more:
- Continental lithosphere versus oceanic lithosphere
brainly.com/question/9817907
-
Oceanic lithosphere is lighter than continental lithosphere
brainly.com/question/2416443
Keywords: LAB, Gutenberg discontinuity, Tonga, seismic, velocity , subduction, magmatism
